Roosvelt, Nazism did not cause the holocaust, people did. Ideas are just ideas, they have benefits and drawbacks. It is a cop-out for someone to blame his actions on some philosophy, be it political, societal, or religious.
In addition you are dead wrong about Osensei's views on bushido. Osensei was a close personal friend of the very people who used bushido to influence young Japanese people to join the military during WWII. Osensei was at least associated with multiple members of a Japanese secret society whose goal was to use bushido to re-glorify the samurai families by creating a class-oriented military hierarchy as the first step to returing to a pre-meiji social structure.